Transducing data using high frequency ferroelectric read demodulation

ABSTRACT

Apparatus and method for transducing data from a ferroelectric data storage medium using high frequency read modulation. In accordance with some embodiments, a ferroelectric data transducer has a write electrode, a doped semiconductor layer with a source, a drain and a channel therebetween, and an insulating layer disposed between the channel and the write electrode. A write circuit applies a time varying write signal at a first frequency to the write electrode to write a corresponding sequence of data bits to an adjacent ferroelectric data storage medium. A read circuit reads the sequence of data bits from the data storage medium by applying a time varying read signal at a higher, second frequency to the write electrode and detecting changes in electrical resistance of the channel.

RELATED APPLICATIONS

This application is a continuation of copending U.S. patent application Ser. No. 12/489,560 filed Jun. 23, 2009 which claims priority to Korean Patent Application No. 10-2008-0059768 filed on Jun. 24, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

Currently, in most hard disk drives (HDDs) installed in personal computers (PCs), information is recorded by a magnetic field. In such a recording medium, a plurality of magnetic domains, which are magnetized in a first or second direction (i.e., the second direction is opposite to the first direction), are formed on a surface of the recording medium, and information “0” or “1” is recorded in each respective magnetic domain.

Recently, research has been conducted with respect to a recording medium and an electric field read/write head which records and reproduces information by an electric field. Such a recording medium has a plurality of electric domains formed on a surface thereof. These electric domains are magnetized in a first or second direction (i.e., the second direction is opposite to the first direction), and information of “0” or “1” is recorded in a respective electric domain.

The electric field read/write head reproduces the recorded information recorded from these electric domains using an electric field generated from the recording medium.

However, there is a need for a method of correctly reading out the information recorded in the recording medium, even if an intensity of the electric field generated from the recording medium is weak and there is noise interference in the electric field. The higher is a density of information written in the recording medium, the smaller is an electric domain generated in the recording medium. Thus, an intensity of an electric field generated in the electric domain also becomes weaker. Accordingly, the need for the above-described method increases due to higher integration of the recording medium.

SUMMARY

Various embodiments of the present disclosure are generally directed to an apparatus and method for Apparatus and method for transducing data from a ferroelectric data storage medium using high frequency read modulation.

In accordance with some embodiments, an apparatus generally comprises a ferroelectric data transducer comprising a write electrode, a doped semiconductor layer having a source, a drain and a channel therebetween, and an insulating layer disposed between the channel and the write electrode. A write circuit is adapted to apply a time varying write signal at a first frequency to the write electrode to write a corresponding sequence of data bits to an adjacent ferroelectric data storage medium. A read circuit adapted to read the sequence of data bits from the data storage medium by applying a time varying read signal at a higher, second frequency to the write electrode and detecting changes in electrical resistance of the channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:

FIG. 1 is a structural view of a recording medium and a header according to an exemplary embodiment;

FIG. 2A is a perspective view of an electric field read/write head illustrated in FIG. 1, according to an exemplary embodiment;

FIG. 2B is a front view of the electric field read/write head illustrated in FIG. 1, according to an exemplary embodiment;

FIG. 3 is a block diagram of an electric field read/write apparatus according to an exemplary embodiment;

FIG. 4 is a reference view illustrating an operation of a modulation unit illustrated in FIG. 3, according to an exemplary embodiment;

FIG. 5 is a circuit diagram of a modified version of a read unit and a demodulation unit illustrated in FIG. 3, according to an exemplary embodiment;

FIG. 6 is a circuit diagram of a modified version of the read unit and the demodulation unit illustrated in FIG. 3, according to another exemplary embodiment; and

FIG. 7 is a flow chart of an electric field read/write method, according to an exemplary embodiment.

DETAILED DESCRIPTION

Exemplary embodiments will now be described more fully with reference to the accompanying drawings. Hereinafter, an electric field according to exemplary embodiments will be described with reference to the attached drawings. Like reference numerals in the drawings denote like elements.

The term “unit”, as used herein, indicates, but is not limited to, a software or hardware component, such as a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks. A unit may advantageously be configured to reside on the addressable storage medium and configured to be executed on one or more processors. Thus, a unit may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided for in the components and units may be combined into fewer components and units or further separated into additional components and units. In addition, the components and units may be implemented such that they execute one or more computers in a communication system.

FIG. 1 is a structural view of a recording medium 100 and an electric field read/write head 110 according to an exemplary embodiment.

The recording medium 100 may be a ferroelectric recording medium, and may be a structure including a substrate, an electrode and a ferroelectric layer which are sequentially stacked. In this case, the substrate may be formed of Si, glass, etc. The electrode may be formed of a metal such as Pt, Al, Au, Ag, Cu, etc. or metal oxide such as LaCoO, and may be grounded. The ferroelectric layer is formed of a ferroelectric material such as PbTiO₃, PbZrO₃, etc.

Information is recorded in the recording medium 100 using an electric field. In the recording medium 100, a plurality of electric domains polarized in a first direction or a second direction (here, the first direction is an opposite direction to the second direction) are formed on a surface of the recording medium 100. Information of “0” or “1” is recorded in these electric domains.

The electric field read/write head 110 may read information written to the recording medium 100 or may write information to the recording medium 100 while floating above a surface of the rotating recording medium 100 with a given space therebetween.

The electric field read/write head 110 is attached to a head suspension 120. The head suspension 120 is disposed at a tip of a swing arm 130. The swing arm 130 is moved by a voice coil motor 140. By virtue of the rotation of the swing arm 130, the electric field read/write head 110 can be positioned over a desired location of the recording medium 100.

FIG. 2A is a perspective view of the electric field read/write head 110 illustrated in FIG. 1, according to an exemplary embodiment. FIG. 2B is a front view of the electric field read/write head 110 illustrated in FIG. 1, according to the exemplary embodiment.

Referring to FIGS. 2A and 2B, the electric field read/write head 110 is embodied on a semiconductor substrate 210 formed of a p-type or n-type semiconductor material. The semiconductor substrate 210 includes a first surface 211 facing the recording medium 100 and a second surface 212 abutting the first surface 211. The first surface 211 and the second surface 212 may be perpendicular to each other.

An air bearing surface (ABS) pattern 230 may be formed on the first surface 211 of the semiconductor substrate 210. The ABS pattern 230 functions such that the electric field read/write head 110 may float above a surface of the recording medium 100.

A channel C that is a low concentration impurity region and a source region S and a drain region D that are high concentration impurity regions are formed on the semiconductor substrate 210. The source region S and the drain region D are disposed on opposite sides of the channel C. A source electrode E1 is electrically connected to the source region S. A drain electrode E2 is electrically connected to the drain region D. When the semiconductor substrate 210 is formed of a p-type semiconductor, the channel C is an n−impurity region, and the source region S and the drain region D are n+ impurity regions. On the other hand, when the semiconductor substrate 210 is formed of an n-type semiconductor, the channel C is a p− impurity region, and the source region S and the drain region D are p+ impurity regions. A first insulating layer 221 is disposed on the channel C. A writing electrode WR is disposed on the first insulating layer 221. A second insulating layer 222 is disposed on an exposed portion of the source region S and an exposed portion of the drain region D.

The channel C provides a path through which a current flows between the source region S and the drain region D. A resistance of the channel C varies according to at least one of a polarization direction and an electric charge of an electric domain facing the channel C. The electric field read/write head 110 detects the resistance of the channel C to read information written in the electric domain facing the channel C.

Thus, a writing operation of the electric field read/write head 110 will be described for reference. When a positive voltage (+) or negative voltage (−) whose absolute value is equal to or greater than a threshold voltage is applied to the writing electrode WR of the electric field read/write head 110, particular information of “0” or “1” is recorded in the electric domain facing the channel C. For example, when a positive (+) voltage equal to or greater than the threshold voltage is applied to the writing electrode WR, the electric domain facing the channel C is polarized in a first direction, and the information of “0” is recorded in the electric domain. In addition, when a negative (−) voltage whose absolute value is equal to or greater than the threshold voltage is applied to the writing electrode WR, the electric domain facing the channel C is polarized in a second direction, and thus information of “1” is recorded in the electric domain.

FIG. 3 is a block diagram of an electric field read/write apparatus according to an exemplary embodiment. The electric field read/write apparatus according to the present exemplary embodiment may include a modulation unit 310, a detection unit 320, a read unit 330 and a demodulation unit 340. In this case, the modulation unit 310, the read unit 330 and demodulation unit 340 may be provided outside of the electric field read/write head 110 illustrated in FIG. 1, and the detection unit 320 may be disposed inside of the electric field read/write head 110 illustrated in FIG. 1.

The modulation unit 310 modulates an electric field generated from the recording medium 100 by using a modulation signal. Since the recording medium 100 operates while data is being read, the electric domain facing the channel C of the electric field read/write head 110 continuously varies. Thus, the modulation unit 310 modulates an electric field variation transition (i.e., an electric field value based on a time sequence) of the electric field which is generated from the electric domain facing the channel C of the electric field read/write head 110 by using the modulation signal. The modulation signal has a given frequency, and is applied to the writing electrode WR of the electric field read/write head 110. The size of the modulation signal may be less than a threshold voltage.

The detection unit 320 detects the electric field variation (more specifically, the electric field variation transition), which is modulated by the modulation unit 310. In particular, the detection unit 320 detects a resistance variation (more specifically, a resistance variation transition) of the channel C occurring due to the electric field modulated by the modulation unit 310.

The read unit 330 outputs a voltage signal determined according to the electric field variation (more specifically, the electric field variation transition), which is detected by the detection unit 320. The read unit 330 is embodied by a plurality of circuitry devices (e.g., a resistor and an amplifier) including the electric field read/write head 110. In addition, the read unit 330 receives a given voltage to output a voltage signal determined according to the electric field variation detected by the detection unit 320. In this case, the circuit devices constituting the read unit 330 may be arranged according to a given design. Thus, the read unit 330 outputs the voltage signal determined according to the electric field variation (more specifically, the electric field variation transition) detected by the detection unit 320 by using a given method.

The demodulation unit 340 demodulates the voltage signal input from the read unit 330 by using the modulation signal used by the modulation unit 310 to generate the electric field from the recording medium 100. According to a demodulation result, the demodulation unit 340 determines information written in the recording medium 100.

The demodulation unit 340 demodulates the voltage signal input from the read unit 330 by using the modulation signal, performs low pass filtering (LPF) with a filter coefficient with respect to the demodulation result, and then determines the information written in the recording medium 100 according to an LPF result. At this time, by performing the LFP with respect to the demodulation result, the demodulation unit 340 may extract only a direct current (DC) component from the LPF result to determine the information written in the recording medium 100 according to the extracted DC component.

The demodulation unit 340 may remove an offset contained in the demodulation result, and may determine the information written in the recording medium 100 according to the demodulation result from which the offset is removed.

In short, the information written in the recording medium 100 is reproduced by detecting a resistance variation of the channel C of the electric field read/write head 110 floating above a surface of the recording medium 100.

A resistance of a resistor can be determined by a voltage or a current of a circuit including the resistor. In this regard, when a voltage signal (or, a current signal) having information regarding a resistance of a resistor is obtained, noise in the circuit may interfere with the voltage signal. Thus, when a voltage signal at a given point of a circuit including a resistor is obtained in order to correctly determine a resistance of the resistor, as much noise as possible in the circuit must be prevented from interfering with the voltage signal.

Accordingly, in order to correctly reproduce the information written in the recording medium 100, a resistance variation of the channel C, dependent on an electric field generated in the recording medium 100, needs to be correctly detected. To achieve this, a voltage signal (or, a current signal) of a circuit including the channel C, which has information regarding the resistance variation of the channel C, needs to be correctly obtained so that as much noise as possible in the circuit can be prevented from interfering with the voltage signal.

According to the present exemplary embodiment, the electric field read/write apparatus according to the present exemplary embodiment does not simply use a voltage signal containing information regarding a resistance variation of the channel C occurring due to an electric field generated in the recording medium 100, in order to reproduce information recorded in the recording medium. Instead, in the present exemplary embodiment, the electric field is first modulated by a modulation signal. Next, a voltage signal containing information regarding a resistance variation of the channel C occurring due to a modulation result is demodulated using the modulation signal, and then information written in the recording medium 100 is reproduced according to a demodulation result. A frequency of the modulation signal is much higher than that of the electric field generated in the recording medium 100, and accordingly, the modulated electric field is nearly completely unaffected by noise. Thus, according to the present exemplary embodiment, since the voltage signal containing information regarding the resistance variation of the channel C occurring due to the electric field modulated by the modulation signal is obtained as a voltage signal that is nearly completely unaffected by the noise in a circuit constituting the read unit 330, the information written in the recording medium 100 may be correctly reproduced.

FIG. 4 is a reference view illustrating an operation of the modulation unit 310 illustrated in FIG. 3, according to an exemplary embodiment. FIG. 4 illustrates a source region S, a drain region D and a channel C of the electric field read/write head 110 illustrated in FIG. 1. Referring to FIG. 4, a current may flow from the drain region D to the source region S through the channel C having width W, thickness T and length L.

The width W of the channel C is determined according to an electric field 410 generated from the recording medium 100. Accordingly, a resistance of the channel C is determined according to the electric field 410 generated in the recording medium 100.

Similarly, since a writing electrode WR is disposed above the first insulating layer 221 disposed above the channel C, the thickness T of the channel C is determined by the modulation signal 420 applied to the writing electrode WR. That is, the resistance of the channel C is affected by the modulation signal 420.

Thus, the resistance of the channel C is given by Equation 1 as follows:

$\begin{matrix} \begin{matrix} {r_{F} = {\rho \frac{L}{A}}} \\ {= {\rho \frac{L}{\left( {W - w} \right)\left( {T - t} \right)}}} \\ {{\approx {\rho \frac{L}{WT}\left( {1 + \frac{w}{W} + \frac{t}{T} - \frac{w^{2}}{W^{2}} - \frac{wt}{WT} - \frac{t^{2}}{T^{2}}} \right)}},} \end{matrix} & (1) \end{matrix}$

where r_(F) is the resistance of the channel C, ρ is the resistivity of the channel C, A is a cross section of the channel C, L is the length of the channel C, W is the width of the channel C, T is the thickness of the channel C, w is the variation in width of the channel C occurring with respect to change in carrier distribution in the channel C due to an electric field generated in the recording medium 100, and t is the variation in thickness of the channel C occurring with respect to carrier distribution in the channel C due to a modulation signal.

When only a component r_(ω) having a frequency w of the modulation signal is extracted from among components of r_(F) of Equation 1, the component r_(ω) can be given by Equation 2:

$\begin{matrix} {r_{\omega} = {\rho \frac{L}{WT}\left( {1 - \frac{w}{W}} \right)\frac{t}{T}}} & (2) \end{matrix}$

FIG. 5 is a circuit diagram of a modified version of the read unit 330 and the demodulation unit 340 illustrated in FIG. 3, according to an exemplary embodiment.

Referring to FIG. 5, a read unit 330A includes a wheatstone bridge circuit and an instrumentation amplifier. The instrumentation amplifier may be implemented using a plurality of ideal operational amplifiers (OP AMPs) to perform a given operation. In FIG. 5 r_(F) is a resistance of the channel C, V_(SS) is a given voltage input to the read unit 330A, R is a resistance, v₁ is a voltage of a non-inverting terminal of the instrumentation amplifier, and v₂ is a voltage of an inverting terminal of the instrumentation amplifier. The instrumentation amplifier amplifies and outputs v_(o), which is A (A is a positive integer) times a difference between v1 and v2. At this time, v_(o) represents the voltage signal determined according to the electric field variation (more specifically, the electric field variation transition) detected by the detection unit 320 as described above.

As illustrated in FIG. 5, a demodulation unit 340A demodulates v_(o) by using a modulation signal v_(t), performs LPF with respect to a demodulation result v_(om)), and determines information written in the recording medium 100 according to a result v_(out) of the LPF.

In particular, v₁, v₂, v_(o), v_(om) and v_(out), as illustrated in FIG. 5, are each given by Equation 3 as follows:

$\begin{matrix} {{v_{1} = {\frac{r_{F}}{P_{t} + r_{F}}V_{SS}}}{v_{2} = {\frac{1}{2}V_{SS}}}{v_{0} = {{A\left( {v_{1} - v_{2}} \right)} = {\frac{1}{2}\frac{r_{F} - P_{t}}{P_{t} + r_{F}}V_{SS}A}}}\begin{matrix} {v_{om} = {\frac{1}{2}\frac{r_{F} - P_{t}}{P_{t} + r_{F}}V_{SS}{Av}_{t}}} \\ {{\approx {{\frac{V_{SS}}{2\left( {P_{t} + r_{0}} \right)}\left\lbrack {r_{0} - P_{t} + r_{\omega} + r_{2\omega}} \right\rbrack}{Av}_{t}}},} \end{matrix}} & (3) \end{matrix}$

where r_(o) is a DC component of r_(F), r_(2ω) is a component having a frequency 2ω that is twice the frequency ω of the modulation signal, extracted from among the components of r_(F). In components of v_(om), (r_(o)*v_(t)) has only a component of ω, (R*v_(t)) has only a component of ω, (rω*v_(t)) has only a DC component and a component of 2ω, and a DC component of (r_(2ω)* v_(t)) has only components of ω and 3ω.

Thus, the demodulation unit 340A may perform LPF with respect to the demodulation result v_(om) to extract only a DC component from the demodulation result v_(om). That is, the demodulation unit 340A may perform LPF with respect to the demodulation result v_(om) to obtain only information regarding (r_(ω)*v_(t)) from among information regarding (r_(o)*v_(t)), (R*v_(t)), (r_(ω)*v_(t)) and (r_(2ω)*v_(t)), and may reproduce information written in the recording medium 100 according to the obtained information.

FIG. 6 is a circuit diagram of a modified version of the read unit 330 and the demodulation unit 340 illustrated in FIG. 3, according to another exemplary embodiment.

As illustrated in FIG. 6, a read unit 330B is embodied using an ideal OP AMP including a closed-loop. Referring to FIG. 6, is a resistance of the channel C, V_(SS) is a given voltage input to read unit 330B, R is a resistance, i₁ is a current flowing through the resistance R connected to a non-inverting terminal of the OP AMP, v₁ is a voltage of a non-inverting terminal of the OP AMP and v_(o) is the voltage signal determined according to the electric field variation (more specifically, the electric field variation transition) detected by the detection unit 320 as described above.

As illustrated in FIG. 6, a demodulation unit 340B demodulates v^(o) by using the modulation signal v_(t), performs LPF with respect to the demodulation result v_(om), and determines information written in the recording medium 100 according to a result v_(out) of the LPF.

In particular, v₁, v₂, v_(o), v_(om) and v_(out), as illustrated in FIG. 6 are each given by Equation 4 as follows:

$\begin{matrix} {{v_{2} = {\frac{1}{2}V_{SS}}}{v_{1} = v_{2}}{i_{1} = {\frac{V_{SS} - v_{2}}{R} = \frac{V_{SS}}{2R}}}{v_{1} = {{r_{F}i_{1}} + v_{0}}}\begin{matrix} {v_{0} = {v_{1} - {r_{F}i_{1}}}} \\ {= {{- \frac{r_{F} - R}{2R}}V_{SS}}} \end{matrix}{{v_{om} = {{- {\frac{V_{SS}}{2R}\left\lbrack {r_{0} - R + r_{\omega} + r_{2\; \omega}} \right\rbrack}}v_{t}}},}} & (4) \end{matrix}$

where r_(o) is a DC component of r_(F) and r_(2ω), is a component having a frequency 2ω that is twice the frequency ω of the modulation signal, extracted from among the components of r_(t). In components v_(om), (r_(o)*v_(t)) has only a component of ω, (R*v_(t)) has only a component of ω, (r_(ω)*v_(t)) has only a DC component and a component of 2ω, and a DC component of (r_(2ω)*v_(t)) has only components of ω and 3ω.

Thus, a demodulation unit 340B may perform LPF with respect to the demodulation result v_(om) to extract only a DC component from the demodulation result v_(om). That is the demodulation unit 340A may perform LPF with respect to the demodulation result v_(om) to obtain only information regarding (r_(ω)*v_(t)) from among information regarding (r_(o)*v_(t)), (R* v_(t)), (r_(ω)*v_(t)) and (r_(2ω)*v_(t)), and may reproduce information written in the recording medium 100 according to the obtained information.

FIG. 7 is a flow chart of an electric field read/write method, according to an exemplary embodiment. The method according to the present exemplary embodiment may include correctly detecting a resistance of a channel, which varies according to an electric field generated from a recording medium in which information is written by an electric field, to correctly reproduce information written in the recording medium (operations 710 through 730). The method of FIG. 7 will be described with reference to FIGS. 1, 2A, 2B, and 3.

The modulation unit 310 modulates an electric field generated from the recording medium 100 by using a given modulation signal (operation 710).

Next, the detection unit 320 detects a variation in the modulated electric field (operation 720). In particular, the detection unit 320 detects a variation in the resistance of the channel C occurring due to the modulated electric field.

The demodulation unit 340 then demodulates a voltage signal determined according to the detected variation by using the modulation signal, and determines information written in the recording medium 100 according to a demodulation result (operation 730).

Computer programs for executing the electric field read/write method according to the exemplary embodiments in a computer can be stored in a computer readable recording medium. Examples of the computer readable recording medium include magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.), and optical recording media (e.g., CD-ROMs, or DVDs). The exemplary embodiments can also be transmitted through a transmission medium, which include carrier waves transmitted through the Internet or various types of communication channel. The computer readable recording medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

While the present disclosure has set forth various exemplary embodiments, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims. 

1. Apparatus comprising: a ferroelectric data transducer comprising a write electrode, a doped semiconductor layer having a source, a drain and a channel therebetween, and an insulating layer disposed between the channel and the write electrode; a write circuit adapted to apply a time varying write signal at a first frequency to the write electrode to write a corresponding sequence of data bits to an adjacent ferroelectric data storage medium; and a read circuit adapted to read the sequence of data bits from the data storage medium by applying a time varying read signal at a higher, second frequency to the write electrode and detecting changes in electrical resistance of the channel.
 2. The apparatus of claim 1, in which the read circuit passes a steady state current through the channel from the source to drain during the application of the time varying read signal to the write electrode and detects the sequence of data bits responsive to changes in resistance of the channel imparted to the channel by respective electric fields from the storage medium.
 3. The apparatus of claim 1, in which the data transducer further comprises a main body having a substantially rectilinear shape, the body having an air bearing surface (ABS) on a first side of the body in facing relation to the storage medium, the data transducer mounted to a second side of the body orthogonal to the first side, the ABS supporting the write electrode in non-contacting relation to the storage medium during application of the time varying write signal.
 4. The apparatus of claim 1, in which the read circuit comprises a modulation circuit, a detector circuit and a demodulation circuit, the detector circuit incorporated into the data transducer and the modulation and demodulation circuits coupled to the data transducer.
 5. The apparatus of claim 4, in which the modulation circuit applies the time varying read signal to the write electrode, the detection circuit amplifies a channel signal responsive to application of current through the channel from the drain to the source, and the demodulation circuit applies filtering to the amplified channel signal from the detection circuit.
 6. The apparatus of claim 1, in which a detection portion of the read circuit is disposed within the data transducer.
 7. The apparatus of claim 1, further comprising said ferroelectric data storage medium, the storage medium comprising a substrate, a ferroelectric layer and an electrode layer disposed between the substrate and the ferroelectric layer, the sequence of data bits written in the form of a plurality of electric field domains polarized in respective first or second directions, respectively.
 8. The apparatus of claim 7, in which the sequence of data bits is detected responsive to the plurality of electric field domains imparting a change in electrical resistance to the channel.
 9. The apparatus of claim 1, in which the read circuit applies low pass filtering and direct current (DC) offset compensation to a read signal from the channel to demodulate the sequence of data bits written to the storage medium.
 10. An apparatus comprising: a ferroelectric data storage medium having a ferroelectric layer adapted to store data in the form of a plurality of electric field domains; a ferroelectric data transducer adapted to be supported adjacent the medium via an air bearing surface (ABS), the data transducer comprising a channel region and a write electrode; and a data read/write circuit adapted to write data to the medium by applying a time varying write signal to the write electrode at a first frequency, and to read data from the medium by applying a time varying read signal to the write electrode at a second, higher frequency and detecting changes in resistance of the channel region.
 11. The apparatus of claim 10, in which the data transducer further comprises a layer of semiconductor material with spaced apart doped regions to form respective source and drain regions on opposing sides of the channel region, and an insulating layer disposed between the channel region and the write electrode to provide a field effect transistor (FET) structure.
 12. The apparatus of claim 10, in which the read/write circuit passes a steady state current through the channel during the application of the time varying read signal to the write electrode and detects a sequence of data bits from the medium responsive to changes in resistance of the channel imparted to the channel by the plurality of electric field domains.
 13. The apparatus of claim 10, in which a detection portion of the read/write circuit is disposed within the data transducer.
 14. The apparatus of claim 13, in which the detection portion amplifies a signal indicative of changes in electrical resistance of the channel, and in which the read/write circuit further comprises a demodulation portion which applies low pass filtering and direct current (DC) offset compensation to the amplified signal from the detection portion.
 15. A method comprising: supporting a ferroelectric data transducer comprising a write electrode and a channel region adjacent a ferroelectric data storage medium having a ferroelectric layer; writing data to the medium responsive to application of a time varying write signal at a first frequency to the write electrode to generate a plurality of electric field domains in the ferroelectric layer; and reading data from the medium responsive to application of a time varying read signal at a second, higher frequency to the write electrode to generate a sequence of bits from the medium responsive to changes in electrical resistance of the channel region imparted by the plurality of electric field domains.
 16. The method of claim 15, in which the writing of data to the medium comprises applying a voltage above a selected threshold level to the write electrode to write a first data state to the medium and applying a voltage below the selected threshold level to the write electrode to write a second, different data state to the medium.
 17. The method of claim 15, in which the reading of data from the medium comprises passing a steady state current through the channel from a drain region to a source region during the application of the time varying read signal to the write electrode and detecting the sequence of data bits from said current as modulated by the time varying read signal and the plurality of electric field domains.
 18. The method of claim 15, in which the reading of data from the medium comprises obtaining a signal indicative of changes in the resistance of the channel region, amplifying the signal to generate an amplified signal, and applying low pass filtering to the amplified signal to generate a filtered signal.
 19. The method of claim 15, in which the reading of data from the medium is carried out by a read circuit, a detection portion of which being disposed within the data transducer.
 20. The method of claim 15, in which the data storage medium is characterized as a rotatable disc, in which the data transducer is supported by a moveable actuator, and in which the supporting of the data transducer comprises rotating the rotatable disc at a selected rotational velocity and positioning the data transducer adjacent the rotatable disc over a selected track using the actuator. 